VoIP is an acronym for Voice over IP, or in more common terms, phone service over IP networks (e.g., the Internet). VoIP offers certain advantages over plain old telephone service (POTS), such as lower cost and increased functionality.
However, VoIP still doesn't provide the same level of service and reliability as POTS. Quality of VoIP can be degraded by sender problems, network problems, receiver problems or any combination of these problems.
Quality analysis is generally based on the analysis of audio payloads. The payloads are used to calculate compact values that represent the user perception of speech quality. This method works on the application level.
An alternative method works on the packet level. During a call between two VoIP devices (e.g., two IP phones), the device that receives an audio stream generates a report every five seconds and sends each report to the device that sent the audio stream. The reports provide feedback to the sending device. For example, RTCP reports provide information about jitter.
However, the jitter information is not accurate, as it is only a snapshot at the time of a report and is not intended to be taken quantitatively. Moreover, the RTCP reports do not explain why the jitter or other problems occurred, nor do they distinguish between network-caused problems and sender-caused problems.